Move mirror::Object setters to ObjPtr

Bug: 31113334

Test: test-art-host

Change-Id: I2c4c84645e194c3c435a4a6fd670176b0e98671f
diff --git a/runtime/mirror/object.cc b/runtime/mirror/object.cc
index 90b97fd..fbb7c96 100644
--- a/runtime/mirror/object.cc
+++ b/runtime/mirror/object.cc
@@ -199,7 +199,7 @@
   UNREACHABLE();
 }
 
-void Object::CheckFieldAssignmentImpl(MemberOffset field_offset, Object* new_value) {
+void Object::CheckFieldAssignmentImpl(MemberOffset field_offset, ObjPtr<Object> new_value) {
   Class* c = GetClass();
   Runtime* runtime = Runtime::Current();
   if (runtime->GetClassLinker() == nullptr || !runtime->IsStarted() ||